Riveting member for assembling composite hardware

ABSTRACT

A fastener is configured to assemble parts of composite materials. The fastener includes a head; a sleeve including a first section including a first inner diameter, and a second section including a second inner diameter, the second inner diameter being less than the first inner diameter, the second section being between the first section and the head. The fastener also includes an insert inside the sleeve.

FIELD OF APPLICATION OF THE INVENTION

The present invention relates to the field of rivets and in particularto adaptations enabling use thereof for fixing composite materials.

DESCRIPTION OF THE PRIOR ART

Fixing composite materials by means of rivets has various constraints,including:

-   -   good fatigue strength of the assemblies must be guaranteed,    -   damage to the composite material when the rivet is fitted must        be avoided,    -   the phenomenon of delamination must be avoided,    -   shear strength must be optimised,    -   tear resistance under traction must be optimised,    -   fitting must not require countersinking at the head,    -   fitting corresponding to that of current solid rivets (by        crushing) must be able to be carried out in order to use        conventional riveting machines,    -   the cost must be improved.

Solid rivets, although inexpensive, are not suitable for fixing partsmade from composite materials. This is because, when it is crushed, thematerial of the rivet bears on the corner or rim of the hole in order toform the bulb (also referred to as the head). This abutment isparticularly high in terms of force and the consequence thereof is thatthe phenomenon of delamination occurs because of the high level ofradial stresses located in the rim of the hole.

Semi-tubular rivets offer a bulb creation requiring less force to formthe head than for a solid rivet but do not offer a fatigue strengthequivalent to that of a solid rivet.

Finally, blind structure fixing rivets providing crimping make itpossible to achieve the majority of the objectives sought but at aparticularly high cost both in terms of manufacture and installationtooling.

DESCRIPTION OF THE INVENTION

Starting from the specification pre-established by the constraintsdefined for fixing in composite materials, the applicant carried outresearch that led to the design of an assembly method for compositematerials and a particularly advantageous riveting member forimplementation thereof.

According to the invention, the method of assembling parts made fromcomposite materials uses a riveting member of the type comprisingfirstly an insert and secondly a sleeve adapted to at least partiallycontain the insert and having an end provided with a head and a tubularend able to be deformed with a view to constituting a bulb on one sideof the materials to be assembled,

-   -   a hole passing through the materials to be assembled being        produced,    -   the sleeve being introduced and held in the hole with its head        in abutment on the rims of the end of the hole and so that its        tubular end projects therefrom on the other side. The method is        remarkable in that it consists of:    -   using a sleeve the hollow core of which has two different        sections, a first section starting from the tubular end to be        deformed having a first diameter and a second section starting        at the end of the first section and with a lesser diameter,    -   using a insert not having a functional axial bearing surface for        purposes of radial swelling of the sleeve in a hole but the        diameter of which is able to allow housing thereof without        deformation in the first section of the hollow core and able to        allow forcible housing thereof in the second section,    -   axially introducing the insert in the sleeve so that the latter        swells radially inside the hole at its small section and the        recess defined by this small section is occupied by said insert,    -   providing, by means of a riveting die, a pressure at the end of        the sleeve to be deformed on its first section in order to        ensure folding thereof by centrifugal radial extension.

This feature is particularly advantageous in that it combines theadvantages of solid rivets with semi-tubular rivets without increasingthe cost thereof.

Thus the swelling of the sleeve within the hole and filling thereof bythe insert will guarantee fatigue strength as well as good shearstrength. In addition, the folding of the tubular end of the sleeve inorder to form the bulb will enable said bulb to be created without greatforce. In addition, given that the folding will start along the lengthof the inserts simultaneously, just before or just after the swellinghas commenced, that is to say when a part of the sleeve comes to belocked in the hole, the axial force imparted will necessarily tend tofold the material of the sleeve part situated outside, that is to saynot gripped inside the hole. Thus the edge on the rivet head side of thehole passing through the materials to be assembled is protected from anydamage. Thus one of the features of the assembly method of the inventionis that it consists of producing a hole without countersinking in thecomposite material on the rivet head side. The time taken and thetooling required for such an operation are thus no longer necessary.

Another feature participating in the protection of the rivet head stemsfrom the fact that the insert has no axial surface with a function ofdeforming the sleeve which, in its axial movement inside the sleeve,makes it possible to have only radial deformations appear. The insertwill not pack the material of the sleeve in the rim of the rivet head.On the contrary, the presence of the insert will serve as a guide to thedeformation of the external part of the sleeve so that folding thereoftakes place uniformly. The production of a bulb under satisfactoryconditions makes it possible to obtain a fixing having good tearstrength. In addition, the configuration of such a riveting member makesit possible to use the tooling conventionally used for fitting a solidrivet.

According to another particularly advantageous feature, the methodconsists of pre-engaging the insert in the first section of the tubularend of the sleeve prior to the engagement of the riveting member in thehole. This feature avoids managing the handling of two parts and makesit possible to use the riveting member of the invention as a solidrivet.

The partial or total swelling of the sleeve part placed inside the holeprovides a first gripping of the sleeve body inside the hole.Nevertheless, in order to optimise fixing, another feature of the methodconsists of continuing the folding until the folded end is crimped onthe insert, which helps to create a structural fixing with optimisedtear strength.

According to another particularly advantageous feature, the assemblymethod of the invention consists of using a sleeve the recess of whichpasses axially right through and inserting the insert through the end ofthe emerging recess of the head.

According to another particularly advantageous feature of the inventionmaking it possible to optimise the locking of the fixing, the assemblymethod of the invention consists of using a sleeve the recess of whichpasses right through it and inserting the insert through the tubular endof the sleeve, the insert comprising dimensions such that its two endsare respectively crimped in the head of the sleeve on the one hand andin the bulb formed by the tubular end of the sleeve on the other hand.

The invention also concerns the riveting member for implementing theassembly method described above.

This riveting member is remarkable in particular in that the recessformed in the tubular part of the sleeve is extended below the head. Inthis configuration, the sleeve has two ends: a closed end equipped witha head and the other end being tubular and emerging, the insertion thentaking place through said distal end.

This feature makes it possible to have available the greatest possiblelength of a sleeve part able to swell in the hole so as to produce aswelling and stressing of the walls of the hole that is as even aspossible. According to another feature, the length of the small sectioncorresponds to the minimum thickness of the elements made from compositematerials to be fixed.

According to another feature, the recess provided in the hole isextended in the head so that the end of the insert can be crimped insaid head in order to optimise locking. According to a preferredembodiment, the cross section of the recess formed in the head is lessthan the cross section with the smallest diameter of the recess formedin the sleeve.

According to another feature, the end of the insert on which the end ofthe folded sleeve is crimped is preformed with a recess that willfacilitate its deformation while requiring less force and allowingdeformation of the material without packing thereof on the edges of thehole. This recess may also be produced on the other end of the insert,which may then have a symmetrical configuration.

Likewise, the crimping can be improved by the external arrangement ofgrooves or flutes on the body of the insert.

Likewise, where one of the ends of the insert is crimped in the head,said end has the form of a cylindrical projection coaxial with the restof the insert and the free end of which is itself provided with a recessfacilitating deformation thereof.

The fundamental concepts of the invention having been disclosed above intheir most elementary form, other details and features will emerge moreclearly from a reading of the following description and with regard tothe accompanying drawings, giving, by way non-limitative example,several embodiments of an assembly method and a riveting memberaccording to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of a view in cross section of the separatesleeve and insert making up a first embodiment of a riveting memberaccording to the invention,

FIG. 2 is a schematic drawing with an external view of the sleeve andinsert assembled with the concealed edges visible,

FIG. 3 is a schematic drawing of an external view of another embodimentof the riveting member,

FIG. 4 is a schematic drawing of an external view of another embodimentof the riveting member,

FIGS. 5, 6, 7, 8 and 9 are views in section of an assembly illustratingthe fitting of the riveting member,

FIGS. 10, 11, 12, 13 and 14 illustrate various embodiments of the insertfor the aforementioned embodiments of the riveting member.

FIGS. 15 and 16 illustrate, in a configuration ready to be fitted and ina configuration once fitted, another embodiment of a riveting memberaccording to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

As illustrated in the drawing in FIG. 1, the riveting member referencedR overall comprises two parts:

-   -   an insert 100,    -   and a sleeve 200 adapted to at least partially contain the        insert and having an end provided with a head 210 and a tubular        end 220 able to be deformed with a view to constituting a bulb        on one side of the materials to be assembled.

In accordance with the invention, the hollow core 230 has two differentsections 231 and 232, that is to say volumes of the cylindricalrecessing having different diameters, a first section 231 starting fromthe tubular end 220 to be deformed having a first diameter D1 and asecond section 232 starting at the end of the first section 231 and witha lesser diameter D2.

These recesses with different diameters match the insert 100 which, nothaving a functional axial bearing surface, has a diameter D3 enabling itto be housed without deformation in the first section 231 of the hollowcore 230 and to enable it to be housed forcibly in the second section232 for purposes of radial swelling of the sleeve 100.

Thus the largest diameter D3 of the insert 100 is less than or slightlygreater than the diameter D1 of the first section in order to enable itto be received without force and without deformation and is larger thanthe diameter D2 of the second section in order to cause the deformationof this sleeve part 200, which will be situated inside the hole passingthrough the parts to be assembled. As illustrated, the second hollowedout section with smaller diameter extends to below the head of thesleeve.

The riveting member is as illustrated by FIGS. 2, 3 and 4, with theinsert 100 pre-engaged in the first part of the tubular core so that itcan be managed as a solid rivet. This pre-engagement is maintained by alight tight mounting between the insert 100 and the first section 231,as illustrated in FIGS. 2 and 3, or by a deformation of the sleeve atthree points 240 disposed at 120 degrees for purposes of clamping of theinsert 100. As illustrated, the insert 100 projects out of the sleeve200 in the pre-engaged position.

FIG. 3 illustrates more specifically a riveting member R′ where thethickness of the sleeve part to be folded 220 is reduced also externallyso that the force necessary for deformation thereof is reduced and theexternal shoulder defined by the separation between the two externalcylinders facilitates and delimits the folding necessary for creatingthe bulb.

The materials used for producing the insert and/or the sleeve can bechosen from those known by the following designations:

-   -   titanium T40,    -   niobium-titanium,    -   stainless steel A286,    -   stainless steel 304L,    -   aluminium and alloys thereof,    -   etc.

According to an embodiment preferred for reasons of saving weight, lowcost and simplicity of implementation, the insert is made from plasticsmaterial. This plastic insert can cooperate with a sleeve made fromtitanium T40.

According to another embodiment preferred for reasons of improved shearstrength and capacity for elongation, the insert is made from grade 9titanium.

The various steps of the assembly implemented by such a riveting memberR will now be described with regard to the drawings in FIGS. 5 to 9.

As illustrated on the drawing in FIG. 5, the riveting member R isdisposed inside a hole T passing through two parts made from compositematerials P1 and P2 to be assembled. The head 210 of the sleeve 200comes into abutment on the external surface of P1 around the hole T. Thediameter of the hole T is such that the body of the sleeve enters insidewith clearance. In addition, the “foldable” portion of the sleeveprojects out of the hole T on the same side as the part P2.

The sleeve head 210 is held in position by means of a fixed riveting die300 and another movable riveting die 400 is disposed on the rivet headside and comes into abutment against the end of the insert 100projecting out of the sleeve 200. In a movement represented by the arrowF1, the movable riveting die 400 exerts an axial pressure against theriveting member R for the purpose of inserting the insert 100, expandingthe sleeve body 200 disposed in the hole, folding the sleeve body 200disposed outside the hole T and crimping the sleeve body 200 on the bodyof the insert 100. In accordance with the invention, the length of thesmall section 232 corresponds substantially to the minimum thickness ofthe parts P1 and P2.

As illustrated in FIG. 6, under the effect of the movement of themovable riveting die 400, the insert 100 starts its forcible insertionin the sleeve body part situated in the hole T. In accordance with theinvention, the effect of this insertion is a radial swelling of thesleeve, in the direction of the arrows F2, which tends to press thesleeve on the walls of the hole T and ensure the filling in of theclearance existing initially between the external periphery of thesleeve 200 and the internal surface of the hole T.

As illustrated in FIG. 7, the advancement of the insert 100 inside thesleeve 200 affords direct contact between the end 220 of the sleeve 200and the movable riveting die 400. Thus, as the internal part of thesleeve swells, the external part of the sleeve is subjected to thepressure of the riveting die 400, which causes the start of thecentrifugal folding by radial expansion in the direction of the arrowsF3 of the external sleeve part 200. The prior swelling of the sleevepart 200 situated inside the hole T blocks any possibility of axialmovement of the material of the sleeve 200 inside the hole T, whichcreates an abutment that will cause the folding of the external part andwhich prevents damage to the rim of the hole T.

As illustrated on the drawing in FIG. 8, while effecting, through itsadapted dimensions, the swelling of the part of the sleeve 200 situatedinside in the hole T, the insert 100 bears at the tubular portion bottomand occupies the whole of the internal recess of this sleeve part 200,thus changing the riveting member R to a configuration of the solidrivet type. By virtue of this configuration, almost all the externalsurface of the sleeve part situated inside the hole T has undergone aswelling, the elastic return of which will be negligible, whichmaintains radial stresses inside the hole T. In addition, the externalend of the sleeve 200 that undergoes the folding is guided during thisoperation by the body of the insert, guaranteeing regularity indeformation.

As illustrated on the drawing in FIG. 9, the continuation of the axialmovement of the riveting die 400 in the direction of the arrow F1 endsthe folding of the sleeve 200 for the creation of a bulb bearing on thepiece P2 around the hole T. In addition, the insert 100 will deform andthe end of the bulb will be crimped on the body of the insert 100 forthe purpose of guaranteeing locking.

In order to facilitate this final deformation as well as the crimping,several embodiments of insert 100 have been imagined. Thus, for example,FIG. 10 shows an insert 100 generally cylindrical in shape, the two ends110 and 120 of which are bevelled externally and the end 120 of which,corresponding to the end on which the sleeve 200 is crimped, comprises arecess 121 facilitating deformation thereof.

FIG. 11 shows an embodiment of an insert 100, the body of which ispreformed with a groove 130 situated close to the end 120 and the twoends of which are provided with a recess.

FIG. 12 shows an insert the body of which is provided over almost allits periphery with a narrowing of its diameter.

FIG. 13 shows an insert 100 the body of which is provided with flutesthat will facilitate crimping.

The embodiments illustrated by the drawings in FIGS. 1, 11, 12 and 13show a recess provided at the two ends of the insert.

Finally, FIG. 14 illustrates a recess 121 allowing deformation of theend 120 of the insert with less force.

As illustrated in the drawings in FIGS. 15 and 16, the riveting memberR3 is equipped with a sleeve 200, the recess 230 of which passes rightthrough it. The adapted insert 100 comprises dimensions such that itstwo ends are respectively crimped in the head of the sleeve 210 on theone hand and in a bulb formed by the tubular end 200 of the sleeve oncefolded on the other hand.

As illustrated, the recess 230 provided in the sleeve 200 is extended inthe head 210 so that the suitably shaped end 140 of the insert 100 canbe crimped in said head 210 in order to optimise locking. Insertion isachieved by the emerging tubular end not equipped with the head.According to the embodiment illustrated, the cross section of the recess211 formed in the head 210 is less than the cross section 232 of smallerdiameter D2 of the recess 230 formed in the sleeve.

The end 140 of the insert that has just been crimped in the head by thetranslation movement represented by the arrow F1 is in the form of acylindrical projection coaxial with the rest of the insert, and the freeend of which is itself provided with a recess facilitating deformationthereof. To accommodate it, the recess 211 formed in the head splays inthe direction of the progression of the insert in the sleeve in order toaccept the volume of the deformed material of the head 140 of the insert100 and thus optimise locking.

It will be understood that the riveting methods and members that havejust been described and depicted above were so described and depictedwith a view to a disclosure rather than a limitation. Naturally variousarrangements, modifications and improvements could be made to the aboveexample without for all that departing from the scope of the invention.

Thus for example, although the embodiment presented illustrates a rivetprovided with a protruding head, the riveting member may be of the typecomprising a sleeve with a countersunk head.

1-15. (canceled)
 16. A fastener configured to assemble parts ofcomposite materials, the fastener comprising: a head; a sleeve includinga first section including a first inner diameter, and a second sectionincluding a second inner diameter, the second inner diameter being lessthan the first inner diameter, the second section being between thefirst section and the head; and an insert inside the sleeve.
 17. Afastener according to claim 16 wherein the head defines a recessabutting the second section of the sleeve.
 18. A fastener according toclaim 16 wherein the first section of the sleeve is configured to form abulb, thereby crimping the insert inside the sleeve.
 19. A fasteneraccording to claim 16 wherein the insert includes a diameter enablinghousing of the insert in the first section without deformation in thefirst section, the diameter being such that housing of the insert in thesecond section causes a swelling of the second section, wherein apressure on the first section enables folding of the first section bycentrifugal radial extension.
 20. A fastener according to claim 16wherein the insert includes a projection, and the head defines a taperedrecess configured to accept deformed material from the projection.
 21. Afastener according to claim 16 wherein the insert defines flutes forfacilitating crimping of the insert within the sleeve.
 22. A fasteneraccording to claim 16 wherein the first section of the sleeve defines afirst outer diameter, the second section of the sleeve defines a secondouter diameter, the second outer diameter being greater than the firstouter diameter.
 23. A fastener according to claim 16 wherein the insertdefines a recess at an end of the insert.
 24. A fastener according toclaim 16 wherein the insert defines a recess at an end of the insert,and another recess at an opposite end of the insert.
 25. A fasteneraccording to claim 16 wherein the insert defines a beveled end.
 26. Afastener according to claim wherein the insert defines an annulargroove.
 27. A fastener according to claim 16 wherein the insert definesa first diameter over a first part of a length of the insert, a seconddiameter over a second part of the length, and a third diameter over athird part of the length, the second diameter being larger than thefirst diameter, the third diameter being larger than the first diameter,the first part being between the second and third parts, the first partconstituting most of the length of the insert.
 28. A fastener accordingto claim 16 wherein the sleeve is made of metal, and the insert is madeof plastic, the insert including a diameter enabling housing of theinsert in the first section without deformation in the first section,the diameter being such that housing of the insert in the second sectioncauses a swelling of the second section, wherein a pressure on the firstsection enables folding of the first section by centrifugal radialextension.
 29. A fastener according to claim 16 wherein the firstsection of the sleeve is configured to form a bulb, thereby crimping theinsert inside the sleeve, wherein the first section of the sleeve isconfigured to engage the insert before forming the bulb, while enablinga part of the insert to project from the sleeve, thereby enabling thehead, sleeve, and insert to be managed as an integrated unit.
 30. Afastener according to claim 16 wherein the first section of the sleeveis configured to form a bulb, thereby crimping the insert inside thesleeve, wherein the first section of the sleeve includes means forengaging the insert before forming the bulb, while enabling a part ofthe insert to project from the sleeve, thereby enabling the head,sleeve, and insert to be managed as an integrated unit.
 31. A fasteneraccording to claim 30 wherein the means for engaging includes aplurality of deformations in the first section of the sleeve.
 32. Afastener configured to assemble parts of composite materials, thefastener comprising: a head; a sleeve including a first section defininga first inner diameter, and a first outer diameter, and a second sectionbetween the first section and the head, the second section defining asecond inner diameter, the second inner diameter being less than thefirst inner diameter, and a second outer diameter, the second outerdiameter being greater than the first outer diameter; and an insertdefining a diameter enabling housing of the insert in the first sectionwithout deformation in the first section, the insert defining a firstend, the first end defining a first recess, and a second end, the secondend defining a projection, the projection defining a second recess,wherein the head defines a head recess configured to accept deformedmaterial from the projection of the insert, wherein housing of theinsert in the second section causes a swelling of the second section,and a pressure on the first section enables folding of the first sectionby centrifugal radial extension thereby crimping the insert inside thesleeve, wherein the first section of the sleeve is configured to engagethe insert before folding, while enabling a part of the insert toproject from the sleeve, thereby enabling the head, sleeve, and insertto be managed as an integrated unit.
 33. A fastener for assembling partsmade from composite materials, the fastener comprising an insert and asleeve adapted to at least partially contain the insert and including anend provided with a head and a tubular end able to be deformed with aview to constituting a bulb on one side of the materials to beassembled, the sleeve being configured to be introduced and held in ahole passing through the materials to be assembled, with the head inabutment on the rims of the end of the hole and so that the tubular endprojects therefrom on the other side, wherein the sleeve comprises ahollow core including two different sections, a first section startingfrom the tubular end to be deformed including a first diameter and asecond section starting at the end of the first section and with alesser diameter, the insert does not have a functional axial bearingsurface for purposes of radial swelling of the sleeve in a hole but thediameter of which enables housing thereof without deformation in thefirst section of the hollow core and enables forcible housing thereof inthe second section, so that when the insert is axially introduced intothe second section, the second section swells radially inside the holeand a recess defined by the second section is occupied by the insert,and when a pressure is provided at the end of the sleeve, the firstsection is deformed in order to ensure folding thereof by centrifugalradial extension.